This invention is an improved stationary collector of light that is especially adapted to collect sunlight. In particular, it is a non-imaging solar concentrator with reflecting sections that may be symmetric or asymmetric and with one or more absorbers.
Non-imaging passive solar collectors have been used for a number of years to gather and use sunlight at elevated temperatures. The term "passive" is taken to mean a collector that can receive and use solar energy at a wide range of angles so that it does not need to be moved to track the sun. Of course, such a collector could also be caused to move if desired.
An example of a non-imaging collector is given in U.S. Pat. No. 5,537,991 entitled "Non-imaging Solar Collector", Winston et al., issued Jul. 23, 1996, which is incorporated here by reference as if set forth fully. The invention taught by that patent is a symmetric reflector with a central heat removal tube and a wedge-shaped absorber that extends from the absorber tube to or nearly to the symmetric reflector. The '991 patent has referred to the wedge-shaped absorber as exhibiting an "ice-cream-cone" geometry because its cross-section resembles an ice cream cone. The '991 patent overcomes some of the disadvantages of the prior art such as having radial fins that lose efficiency through re-radiation and also such as having non-concentrically disposed heat removal tubes. The '991 patent, however, has symmetric reflectors that place limits on their collection versatility over a range of angles of incidence of sunlight. It also has a wedge-shaped collector that extends from a central heat removal tube directly downward to the reflector. This also creates certain disadvantages in collection. The current state of the art is summarized in U.S. Pat. No. 5,586,013, entitled "Nonimaging Optical Illumination System," U.S. Pat. No. 5,816,693, entitled "Nonimaging Optical Illumination System," and U.S. Pat. No. 5,610,768, entitled "Nonimaging Radiant Energy Device."
When solar collectors are used, the radiant flux that they concentrate can create problems if the heat is not removed from the region of the absorber. This may happen, for example, if a pump circulating a coolant through the collector fails. If steps are not taken quickly, the collector may be damaged or even destroyed.
It is an object of the present invention to make a better passive solar collector.
It is a further object of the present invention to provide a passive solar collector that will maximize collection of solar energy at times of day when the air-conditioning load is at or near a maximum.
It is a further object of the present invention to provide a passive solar collector that will absorb a maximum amount of solar radiation and reradiate a minimum amount.
It is a further object of the present invention to provide a passive solar collector that is protected against excessive temperatures without the need for human intervention.
It is a further object of the present invention to provide a solar collector that includes as an absorber a thermos-bottle configuration.
It is a further object of the invention to provide an improved method and apparatus for producing a user-selected non-imaging optical output from natural light sources.
It is a further object of the invention to provide a novel method and apparatus for providing user-selected non-imaging optical output of light energy from optical designs by controlling edge rays of a light source.
Other objects will become apparent in the course of a detailed description of the invention.